If your rollover check valve rusts out (common problem)(bottom picture/black), a reasonable replacement can be had from a 93/94 (possibly 93-97) Nissan Altima, the Nissan one mounts on the front of the fuel tank but it is a close approximation of the size and shape of the stock Jeep one.

If your nipple breaks off (the top piece) you can drill out the old nipple hole and put in a small brass tube, & a tight press fit, then telescoped several other sizes over that to get to the right diameter for the hose to fit on. Solder all the telescoped tubes together (removed it from the plastic housing for soldering!).

While you are at it, replace the o-ring between the snap-on top of the valve and the valve body, they dry out and wont seal any more, double check it.

P.S. U can also purchase one from here - http://www.willys.net/html/fuel.html